The drainage and irrigation pump station is a complex provided for irrigation and drainage for pumping devices, buildings where the water flows in and out, pumping houses and accessorial devices thereof. The flap valve which is one of the important parts of the drainage and irrigation pump station is an accessorial device for flow closure during the water pump stop time of the drainage and irrigation pump station, and the main function of the flap valve is to stop river water from flowing backwards. At present, common flap valves comprise cast-iron flap valves hung with balanced hammer, floating box flap valves and side-turn-over flap valves, and the floating box flap valves are used most commonly. Usually, the floating box flap valves comprise circular floating box flap valves and quadrate floating box flap valves, as to the latter, the quadrate floating box flap valves comprise generally a valve leaf (as to the large-scale flap valves with the larger size, each valve leaf generally comprises an upper valve leaf and a lower valve leaf), a valve seat and a hinge support. The upper valve leaf and the lower valve leaf are hinge-connected to each other and the upper valve leaf is hinge-connected to the hinge support, and the valve leaf is hermetically connected to the valve seat. The flap valve is closed when the pump of the pump station is stopped, and when the pump is started, the flap valve is opened through the force of water.
However, as to large-scale floating box flap valve (as to flap valves generally larger than 3×3 meters), the shortcomings of the structure are as follows:
1) As to the large-scale flap valves, with larger size, weight of the valve leaf is gradually increased. Therefore, when the flap valve is closed, i.e., the valve leaf is folded, and the impact force between the valve leaves and the valve seat is gradually increased. Thus, the water sealing rubbers used for sealing the valve leaf and valve seat are damaged seriously, thereby resulting in the water sealing rubber is changed frequently and the cost is correspondingly increased. Meanwhile, great noise is made when the heavy valve leaf is striking the valve seat, thereby having an effect on the working environment of the pump station.
2) The sealing structure of the valve leaf and the valve seat in the prior art is as follows: two pieces of mounting plates with the same size are weld upon and under the valve seat. Through holes are bored on the mounting plates, and at the time of assembling, the water sealing rubber whose one end is turned up is placed between the two pieces of mounting plates. Bolts passing through the through holes on the mounting plates are screwed with nuts, and there are plenty of sealing structures on both sides of the valve seat respectively. In other words, it is needed to bore many through holes. Therefore, the assembling processes of these structures are complicated. Meanwhile, compression of the water sealing rubber is small, and as the size of the valve leaf is increased, only the compression of the water sealing rubber can not meet the sealing requirement between the valve leaf and the valve seat.
3) In the prior art, usually, a round hole is provided at the place on the hinge support where the upper valve leaf and the hinge support are hinged, and the upper valve leaf is hinged in the round hole through a pin shaft. Usually, this structure limits the hinged point of the upper valve leaf in a certain place and is immovable, but the whole valve leaf has a length size, with the increasing size of the valve leaf, the seal effect near the valve leaf and the valve seat is fairish, however, the seal effect farther from the valve leaf and the valve seat is very poor, thereby resulting in leakage.
4) In the prior art, scale between the upper valve leaf and the lower valve leaf of the valve leaf generally is that the upper valve leaf is big while the lower valve leaf is small. Thus, when river flow is not so great, the lower valve leaf is opened first. At the time of flow increasing, then the upper valve leaf is opened. However, in the condition of the small lower valve leaf, usually, the small lower valve leaf always can not meet the flow requirement at all, so it is always to open the upper valve leaf again, thereby resulting in great energy consumption and against energy saving.